Add defaults

Author: matthewelwell

flagsmith/flagsmith.py

@@ -11,32 +11,27 @@
 
 from flagsmith.analytics import AnalyticsProcessor
 from flagsmith.exceptions import FlagsmithAPIError, FlagsmithClientError
-from flagsmith.models import Flags
+from flagsmith.models import DefaultFlag, Flags
 from flagsmith.polling_manager import EnvironmentDataPollingManager
 from flagsmith.utils.identities import generate_identities_data
 
 logger = logging.getLogger(__name__)
 
-API_URL = "https://api.flagsmith.com/api/v1/"
-FLAGS_ENDPOINT = "flags/"
-IDENTITY_ENDPOINT = "identities/"
-TRAITS_ENDPOINT = "traits/"
-
-# TODO:
-#    - defaults
+DEFAULT_API_URL = "https://api.flagsmith.com/api/v1/"
 
 
 class Flagsmith:
     def __init__(
         self,
         environment_key: str,
-        api_url: str = API_URL,
+        api_url: str = DEFAULT_API_URL,
         custom_headers: typing.Dict[str, typing.Any] = None,
         request_timeout: int = None,
         enable_client_side_evaluation: bool = False,
         environment_refresh_interval_seconds: int = 60,
         retries: Retry = None,
         enable_analytics: bool = False,
+        defaults: typing.List[DefaultFlag] = None,
     ):
         self.session = requests.Session()
         self.session.headers.update(
@@ -70,6 +65,8 @@ def __init__(
             else None
         )
 
+        self.defaults = defaults or []
+
     def get_environment_flags(self) -> Flags:
         """
         Get all the default for flags for the current environment.
@@ -110,6 +107,7 @@ def _get_environment_flags_from_document(self) -> Flags:
         return Flags.from_feature_state_models(
             feature_states=engine.get_environment_feature_states(self._environment),
             analytics_processor=self._analytics_processor,
+            defaults=self.defaults,
         )
 
     def _get_identity_flags_from_document(
@@ -123,12 +121,18 @@ def _get_identity_flags_from_document(
             feature_states=feature_states,
             analytics_processor=self._analytics_processor,
             identity_id=identity_model.composite_key,
+            defaults=self.defaults,
         )
 
     def _get_environment_flags_from_api(self) -> Flags:
+        api_flags = self._get_json_response(
+            url=self.environment_flags_url, method="GET"
+        )
+
         return Flags.from_api_flags(
-            flags=self._get_json_response(url=self.environment_flags_url, method="GET"),
+            api_flags=api_flags,
             analytics_processor=self._analytics_processor,
+            defaults=self.defaults,
         )
 
     def _get_identity_flags_from_api(
@@ -139,7 +143,9 @@ def _get_identity_flags_from_api(
             url=self.identities_url, method="POST", body=data
         )
         return Flags.from_api_flags(
-            flags=json_response["flags"], analytics_processor=self._analytics_processor
+            api_flags=json_response["flags"],
+            analytics_processor=self._analytics_processor,
+            defaults=self.defaults,
         )
 
     def _get_json_response(self, url: str, method: str, body: dict = None):

flagsmith/models.py

@@ -8,11 +8,21 @@
 
 
 @dataclass
-class Flag:
+class BaseFlag:
     enabled: bool
     value: typing.Any
     feature_name: str
+
+
+@dataclass
+class DefaultFlag(BaseFlag):
+    is_default = True
+
+
+@dataclass
+class Flag(BaseFlag):
     feature_id: int
+    is_default = False
 
     @classmethod
     def from_feature_state_model(
@@ -37,7 +47,7 @@ def from_api_flag(cls, flag_data: dict) -> "Flag":
 
 @dataclass
 class Flags:
-    flags: typing.Dict[str, Flag]
+    flags: typing.Dict[str, BaseFlag]
     _analytics_processor: AnalyticsProcessor = None
 
     @classmethod
@@ -46,30 +56,38 @@ def from_feature_state_models(
         feature_states: typing.List[FeatureStateModel],
         analytics_processor: AnalyticsProcessor,
         identity_id: typing.Any = None,
+        defaults: typing.List[DefaultFlag] = None,
     ) -> "Flags":
-        return cls(
-            flags={
-                feature_state.feature.name: Flag.from_feature_state_model(
-                    feature_state, identity_id=identity_id
-                )
-                for feature_state in feature_states
-            },
-            _analytics_processor=analytics_processor,
-        )
+        flags = {
+            feature_state.feature.name: Flag.from_feature_state_model(
+                feature_state, identity_id=identity_id
+            )
+            for feature_state in feature_states
+        }
+
+        for default in defaults or []:
+            flags.setdefault(default.feature_name, default)
+
+        return cls(flags=flags, _analytics_processor=analytics_processor)
 
     @classmethod
     def from_api_flags(
-        cls, flags: typing.List[dict], analytics_processor: AnalyticsProcessor
+        cls,
+        api_flags: typing.List[dict],
+        analytics_processor: AnalyticsProcessor,
+        defaults: typing.List[DefaultFlag] = None,
     ) -> "Flags":
-        return cls(
-            flags={
-                flag_data["feature"]["name"]: Flag.from_api_flag(flag_data)
-                for flag_data in flags
-            },
-            _analytics_processor=analytics_processor,
-        )
+        flags = {
+            flag_data["feature"]["name"]: Flag.from_api_flag(flag_data)
+            for flag_data in api_flags
+        }
+
+        for default in defaults or []:
+            flags.setdefault(default.feature_name, default)
+
+        return cls(flags=flags, _analytics_processor=analytics_processor)
 
-    def all_flags(self) -> typing.List[Flag]:
+    def all_flags(self) -> typing.List[BaseFlag]:
         """
         Get a list of all Flag objects.
 
@@ -97,7 +115,7 @@ def get_feature_value(self, feature_name: str) -> typing.Any:
         """
         return self.get_flag(feature_name).value
 
-    def get_flag(self, feature_name: str) -> typing.Optional[Flag]:
+    def get_flag(self, feature_name: str) -> typing.Optional[BaseFlag]:
         """
         Get a specific flag given the feature name.
 
@@ -110,7 +128,7 @@ def get_flag(self, feature_name: str) -> typing.Optional[Flag]:
         except KeyError:
             raise FlagsmithClientError("Feature does not exist: %s" % feature_name)
 
-        if self._analytics_processor:
+        if self._analytics_processor and hasattr(flag, "feature_id"):
             self._analytics_processor.track_feature(flag.feature_id)
 
         return flag

tests/test_flagsmith.py

@@ -8,6 +8,7 @@
 
 from flagsmith import Flagsmith
 from flagsmith.exceptions import FlagsmithAPIError
+from flagsmith.models import DefaultFlag
 
 
 def test_flagsmith_starts_polling_manager_on_init_if_enabled(mocker, api_key):
@@ -188,3 +189,100 @@ def test_non_200_response_raises_flagsmith_api_error(flagsmith):
 
     # Then
     # expected exception raised
+
+
+@responses.activate()
+def test_default_flag_is_used_when_no_environment_flags_returned(api_key):
+    # Given
+    # a default flag
+    default_flag = DefaultFlag(
+        enabled=True, value="some-default-value", feature_name="some_feature"
+    )
+    flagsmith = Flagsmith(environment_key=api_key, defaults=[default_flag])
+
+    # and we mock the API to return an empty list of flags
+    responses.add(
+        url=flagsmith.environment_flags_url, method="GET", body=json.dumps([])
+    )
+
+    # When
+    flags = flagsmith.get_environment_flags()
+
+    # Then
+    # the data from the default flag is used
+    flag = flags.get_flag(default_flag.feature_name)
+    assert flag.enabled == default_flag.enabled
+    assert flag.value == default_flag.value
+    assert flag.feature_name == default_flag.feature_name
+
+
+@responses.activate()
+def test_default_flag_is_not_used_when_environment_flags_returned(api_key, flags_json):
+    # Given
+    # A default flag
+    default_flag = DefaultFlag(
+        enabled=True, value="some-default-value", feature_name="some_feature"
+    )
+    flagsmith = Flagsmith(environment_key=api_key, defaults=[default_flag])
+
+    # but we mock the API to return an actual value for the same feature
+    responses.add(url=flagsmith.environment_flags_url, method="GET", body=flags_json)
+
+    # When
+    flags = flagsmith.get_environment_flags()
+
+    # Then
+    # the data from the API response is used, not the default flag
+    flag = flags.get_flag(default_flag.feature_name)
+    assert flag.value != default_flag.value
+    assert flag.value == "some-value"  # hard coded value in tests/data/flags.json
+
+
+@responses.activate()
+def test_default_flag_is_used_when_no_identity_flags_returned(api_key):
+    # Given
+    # a default flag
+    default_flag = DefaultFlag(
+        enabled=True, value="some-default-value", feature_name="some_feature"
+    )
+    flagsmith = Flagsmith(environment_key=api_key, defaults=[default_flag])
+
+    # and we mock the API to return an empty list of flags
+    response_data = {"flags": [], "traits": []}
+    responses.add(
+        url=flagsmith.identities_url, method="POST", body=json.dumps(response_data)
+    )
+
+    # When
+    flags = flagsmith.get_identity_flags(identifier="identifier")
+
+    # Then
+    # the data from the default flag is used
+    flag = flags.get_flag(default_flag.feature_name)
+    assert flag.enabled == default_flag.enabled
+    assert flag.value == default_flag.value
+    assert flag.feature_name == default_flag.feature_name
+
+
+@responses.activate()
+def test_default_flag_is_not_used_when_identity_flags_returned(
+    api_key, identities_json
+):
+    # Given
+    # A default flag
+    default_flag = DefaultFlag(
+        enabled=True, value="some-default-value", feature_name="some_feature"
+    )
+    flagsmith = Flagsmith(environment_key=api_key, defaults=[default_flag])
+
+    # but we mock the API to return an actual value for the same feature
+    responses.add(url=flagsmith.identities_url, method="POST", body=identities_json)
+
+    # When
+    flags = flagsmith.get_identity_flags(identifier="identifier")
+
+    # Then
+    # the data from the API response is used, not the default flag
+    flag = flags.get_flag(default_flag.feature_name)
+    assert flag.value != default_flag.value
+    assert flag.value == "some-value"  # hard coded value in tests/data/identities.json